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Old 8th May 2013, 07:40 PM   #21
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Ok I got it I think.

Quote:
The Two NTCs can be bolted to any part of the chassis. They do not need to meet up with any of the other chassis connected wires.
So, I can leave the two NTC's in place? Each PSU will have its own NTC connected to chassis at two different spots? Do these then need to be connected to star ground, or left only connected to chassis?
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Old 9th May 2013, 03:13 AM   #22
omishra is offline omishra  India
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Quote:
Originally Posted by basi View Post
This is Star Grounding.P.S Remove your black and blue wire between amp boards.

Click the image to open in full size.
Those yellow wires are incorrect!

From RCA it's showing connection to earth ground. The simple solution is carry grounds like this -
From PS to amp board (for each channel)
From Speaker to amp board (for each channel)
From Isolated in RCA to amp board (for each channel)
From earth ground to chassis
From one PS board ground to another PS board ground.
From either PS (and through CL-60) to chassis bolt grounded to mains earth
From transformer shield to chassis grounded bolt, correct in diagram.

Additionally if you connect both RCA grounds together at RCA - RCA still it won't hurt.
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Old 9th May 2013, 08:30 AM   #23
AndrewT is offline AndrewT  Scotland
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The transformer shield MUST be connected to Chassis right beside where the shield comes out of the transformer using the shortest possible length of connector.

The NTC used as a Disconnecter between Main Audio Ground and Chassis may work adequately, since Pass recommends this. I have never seen a report on how effective the NTC is at passing Fault Current.

The PE should be connected to Chassis PERMANENTLY where it enters the Chassis. This connection should never be broken.
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Old 9th May 2013, 09:57 AM   #24
basi is offline basi  Croatia
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Click the image to open in full size.

Ground wires from amp boards to copper plate must be as short as possible.
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Marantz rules
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Old 9th May 2013, 10:09 AM   #25
AndrewT is offline AndrewT  Scotland
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NO !!!!!
the PE MUST be bolted, or welded, directly to the Chassis.
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Old 9th May 2013, 11:17 AM   #26
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OK it seems there are different methods of going about this..

PE will be bolted to chassis using the method mentioned in Fig. 3 of the article mentioned above. Transformer shield will be connected to chassis with shortest wire possible.

Quote:
NO !!!!!
AndrewT, do you agree with the most recent diagram from basi? With PE bolted to chassis then through CL-60 to the isolated star point?

There have been many ideas and i really appreciate it but it is hard for me to decipher which is the most effective.
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Old 9th May 2013, 01:26 PM   #27
AndrewT is offline AndrewT  Scotland
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Basi' shows the PE going through the CL60 to the MAG.
If he meant different, then he needs to show different.
What he has shown is dangerous and potentially lethal.
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Last edited by AndrewT; 9th May 2013 at 01:43 PM.
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Old 9th May 2013, 01:39 PM   #28
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I have been looking at the F5 thread (and others) for a couple of hours now. It seems that there are a lot of different ways to go about doing this..

Should I direct Signal Ground to Amp board via twisted pair, then Amp PCB GND to Main Audio Ground?? Or Sig ground (from RCA Jack) direct to MAG?

Main Audio Ground will be totally isolated from chassis (no contact) and connected through CL-60 to the Chassis Earth bolt..

Can I connect one PSU GND to the other PSU GND then connect them to Main Audio Ground through a single CL-60. Or is the CL-60 not required.

I am sorry for the confusion guys.. I am almost there, I promise
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Old 9th May 2013, 01:42 PM   #29
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Earth (from the wall/IEC socket) will be bolted/soldered direct to chassis with 10 AWG wire. from this point there will be a CL-60 to the isolated MAG.

My question lie in the connections to MAG.
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Old 9th May 2013, 02:31 PM   #30
omishra is offline omishra  India
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This problem does not come when you use 2 dual secondary transformer for 2 PS or single transformer with quad secondaries for 2 PS.

Quote:
Earth (from the wall/IEC socket) will be bolted/soldered direct to chassis with 10 AWG wire. from this point there will be a CL-60 to the isolated MAG.
^^This is correct.

If you used only one dual transformer then you should have only one audio ground (MAG). Though you have 2 sets of PS (including its own rectifiers), still you have same ground referred at two output of PS. But this could lead minor difference at ground level of both PS output, thanks to tolerances of bridge rectifier diodes of both PS.

It would be get connected through input RCA ground of source or preamp, and conduct ground current proportional to difference of ground levels and ripple present. Thus evolve ground loop infringing input signal and amplified through amplifier. So get it corrected by connecting PS ground of both boards together near output of both PS boards, making single MAG.

From this central MAG all ground paths lead to Amp Board. RCA input ground ends on Amp board. Speaker ground terminates at Amp board or MAG star ground, does not matter.

Last edited by omishra; 9th May 2013 at 02:38 PM.
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